Structural mutants of human hemoglobin generally occur in smaller amounts than normal hemoglobin (HbA) in the blood of heterozygous subjects. In thalassemia there is an imbalance in the synthesis of the alpha and beta globin polypeptide chains. This study involves an investigation into the abnormal synthesis of several hemoglobin mutants. One abnormal hemoglobin appears to be synthesized in greater amounts than HbA and another structural mutant is associated with a thalassemia-imbalance in alpha and beta globin production. Investigation of mRNA function in a cell-free system and estimation of cellular mRNA content is contemplated. The objective is to delineate the factors determining differential synthesis of structural hemoglobin variants.